‘Nature’s God’ by Matthew Stewart

Edel Rodriguez for the bston globe

“The Government of the United States of America is not, in any sense, founded on the Christian religion.” So begins Article XI of the 1797 Treaty of Tripoli, which was read aloud in the US Senate and ratified unanimously. Our second president, John Adams, who detested the “spirit of dogmatism and bigotry in clergy and laity” and regarded the resurrection of Jesus as “an absurdity,” promptly signed the treaty into law. It was no big deal then. So why does it all sound so surprising now?

Matthew Stewart’s enthralling and important new book, “Nature’s God: The Heretical Origins of the American Republic,’’ argues that we misremember the philosophical and religious origins of the American Revolution. Stewart, who holds a PhD in philosophy from Oxford University, is the author of previous books on the history of Western philosophy, and once again he happily rips into the original sources of Enlightenment thought, this time discovering a radical and profoundly humanistic worldview underlying the American Revolution.

The book is a pleasure to read, its often surprising conclusions supported by elegant prose and more than 1,000 footnotes. Stewart’s erudite analysis confidently rebuts the creeping campaign of Christian nationalism to “ ‘take back’ the nation and make it what it never in fact was.” The next time someone like Jerry Falwell asserts that the United States is “a Christian nation,” he’ll have to answer to “Nature’s God.’’

The United States, Stewart writes, was in fact founded by a “club of radical philosophers and their fellow travelers” who were known as deists in their day and today would be called “humanists, atheists, pantheists, freethinkers, [or] Universalists.” “America’s revolutionary deism remains an uncomfortable and underreported topic,” writes Stewart, and in his view the Revolutionary leaders — famous men like Thomas Jefferson and Benjamin Franklin, as well as “Forgotten Founding Fathers” such as Thomas Young, one of the organizers of the Boston Tea Party — are themselves partly to blame, since for the most part they veiled their religious unorthodoxy for fear of condemnation.

Franklin, for example, urged his friend Ezra Stiles not to “expose me to Criticism and censure” by making his deistic beliefs known. George Washington, who refused to kneel in church or to take communion, simply declined to answer when asked by clerics whether he believed in the Lord Jesus Christ. “[T]he old fox was too cunning for them,” his friend and fellow freethinker Jefferson noted approvingly.

Does it matter in what or in whom the men who wrote our nation’s founding documents believed? After all, we still have the documents; surely those speak for themselves. Yet over 200 years later we are more absorbed with questions about original intent than ever, and the debate in particular over religious freedom — and freedom from religion — grows louder every day. “Nature’s God’’ makes significant new contributions to our understanding of what the founders had in mind.

As Stewart points out, the “broad plurality of people in America remained active and observant within some variety or other of relatively orthodox religion,” and the radical humanism of the Revolutionary leaders “was simply not representative of its people in this respect.” Jefferson nevertheless believed that the Declaration of Independence would inspire people “to burst the chains under which monkish ignorance and superstition had persuaded them to bind themselves, and to assume the blessings and security of self-government.” His views on religion may have differed from most of his countrymen, but in the end he was the one planning and writing the Declaration.

It was Jefferson, too, who invoked “Nature’s God” in the Declaration of Independence’s first sentence. But this was not “the fictitious, meddling deity of the religious imagination but . . . nature itself or the universe comprehended as a whole. It is a way of talking about God long after God is dead.” This is Nature as God, the “presiding deity of the American Revolution.”

To uncover the origins of this revolutionary philosophy, Stewart embarks on a deep investigation into the history of ideas. Just as Stephen Greenblatt argued in 2011’s historical blockbuster, “The Swerve,’’ Stewart cites the the “revival of Epicurean philosophy that followed upon the rediscovery of Lucretius in early modern Europe” as “the decisive episode in the history of modern thought.” He then follows “Epicurus’s dangerous idea” to the 13 Colonies, where its inherently secular, materialist message focused on the importance of attaining a peaceful, happy life during this lifetime, not after death, and inspired a vision of a nation founded on reason, not on faith.

He finds ample evidence of Epicurean influence in the writings of known intellectuals such as Jefferson and Franklin and in some unexpected places, too. “Oracles of Reason’’ (1784), the almost completely forgotten philosophical manifesto of the American revolutionary Ethan Allen, “testifies to the presence in the remotest regions of revolutionary America of modes of thought that have almost universally been regarded as too old, too radical, and too continental to have played a role in the foundation of the American republic.” The thrill Stewart feels upon its discovery is infectious. “Opening its pages,” he exults, “is like discovering an empty bottle of whisky on the moon.”

When he stepped down from his position as commander of the Continental Army in 1783, Washington made a point of reminding his countrymen: “The foundation of our empire was not laid in the gloomy age of Ignorance and Superstition.” The question “Nature’s God’’ implicitly asks is whether we ought to take Washington at his word.